放射性物质
参考答案:
是指能够产生放射性以及辐射的元素及其化合物,它们在自身的转变过程中会放出射线、射线中的一种或两种,对周围的介质或机体产生电离作用,造成放射性污染或危害。
(51) is a six bytes OSI layer 2 address which is burned into every networking device that provides its unique identity for point to point communication. (52) is a professional organization of individuals in multiple professions which focuses on effort on lower-layer protocols. (53) functions with two layers of protocols. It can connect networks of different speeds and can be adapted to an environment as it expands. (54) is the popular LAN developed under the direction of the IEEE802.5. (55) is the popular backbone technology for transmitting information at high speed with a high level of fault tolerance which is developed under the direction of ANSI.
A.The hub
B.The bridge
C.The router
D.The proxy
下列正常婴儿头颅平片哪些是正确的:()
A.可见到颅缝
B.前囟闭合的时间为1岁6个月
C.后囟闭合的时间为1岁6个月
D.3~4岁时,鞍背、后床突开始骨化
E.见不到松果体钙化